Enhanced Privacy Identification (EPID) is a digital signature scheme. A group public key in EPID corresponds to multiple private keys. A private key can be used to generate a signature. The signature can be verified using the group public key.
EPID is an extension of Direct Anonymous Attestation (DAA). DAA is a cryptographic scheme for providing anonymous signatures. DAA is used for the Trusted Platform Module created by the Trusted Computing Group.
A feature of EPID is that keys issued can be blind. The issuer need not know a member's private key. The EPID signatures are anonymous. The EPID signature cannot be opened to identify the member. The linkability of an EPID signature and members of a group depend upon the base values that are chosen and revealed during the signature. Signatures using a common name verifier can be linked. A signature using a random base name cannot be linked across bases but can be linked within the same base name. Signatures using different base name verifiers cannot be linked. EPID signatures, private keys, and public keys can be revoked.
Radio frequency identification (RFID) includes the wireless use of electromagnetic fields to transfer data. RFID may be implemented through RFID tags that report information to RFID readers.